The CRT has been the dominant technology in the information display field. This has been due in part to the fact that the raster CRT was developed for TV and was readily adapted for digital information displays when the need arose. The CRT has the advantages of a bright, phosphor screen with full color capability and reasonable cost. However, the three-dimensional space requirements and the serial nature of the CRT, which restricts both the resolution and the refresh rate, have disadvantages. In addition, the narrow band width has posed problems in transmitting and displaying the image. These characteristics of the CRT have created a need in the industry for an alternate form of display.
Flat panel displays have a number of inherent advantages over CRTs for the display of an image, whether video or data, in that the image is well focused over the entire display area and the addressing of the display surface is done in a parallel fashion and is amenable to the use of digital circuitry. In addition, the flat panel displays are compact and easily portable, they are simple to mount in horizontal or vertical surfaces, and the position can be easily adjusted to accomodate the desires of the individual operator. Recent advances in integrated circuit technology, wherein more complex circuitry is now available in smaller dimensions and at reduced cost, have made their use in displays more desirable. Current flat panel display technology utilizes integrated circuit technology, but requires the use of high voltage drivers. A variety of technological approaches have been proposed in pursuit of a practical flat panel display, including plasma, electroluminescent, gas electron phosphor and liquid crystal devices. Of these, the ac plasma and electroluminescent devices have attracted particular interest, but the use of either for high resolution display has been limited by the fact that full color is difficult to achieve and the voltage levels required to achieve the desired levels of contrast and brightness have necessitated large, special purpose integrated circuits for the drivers. The resultant cost has made such displays unattractive for all competitive applications where cost is a consideration. Liquid crystal displays operate at low voltage, but as the resolution and density increase the drive complexity correspondingly increases. In addition, liquid crystals have slow response times, limited operating temperature range and limited ability to produce color.
The conventional ac plasma display panel consists of two glass plates hermetically sealed around the periphery. A narrow gas chamber is maintained between the plates, which is filled with a mixture of neon-argon gas. Orthogonal conductors are printed on the interior surfaces of the glass plates, which are subsequently covered with a thin dielectric layer overcoated with magnesium oxide. When the proper ac voltages are applied between orthogonal conductors, a plasma discharge occurs at the selected conductor intersection. This emits light and forms a pixel (picture element).
A plasma that serves as an electron source, rather than a light source, has been developed by Siemens, A.G. and described in Electronics, Dec. 15, 1982, pages 128-130. This plasma-discharge flat panel includes an electron source, a control plate having orthogonal control electrodes deposited on opposite surfaces thereof, and a phosphor target all packaged in a hermetically sealed, glass enclosure. An acceleration electrode is energized with about 4000 v to draw electrons from the continuous dc plasma discharge between the rear cathode and anodic rows on the control plate. The electrons are accelerated through holes located at each intersection of the electrodes on the control plate to excite phosphors on the target. The potential applied at each intersection is controlled with a 50 v bias to govern the total electron current streaming through each hole. Special integrated circuits using double-implanted MOS technology handle the 50 volt pulses at the frequency needed for proper image construction.